My Alpha CB28 CH circuit is getting very hot even with the CH thermostat on the control panel turned down very low.
Typically I set the CH thermostat in the range 2-4 and the pressure runs between 1 and 1.5 bar.
The behaviour now is that with the CH thermostat at 2 the rads are getting very hot and pressure rises up to 2 bar. Pressure actually seems to be nudging up slowly beyond there. Sometimes turning the thermostat down to zero stops the beast running, but sometimes it needs to be turned off and reset. I've not let it run to an overheat, nor do I know for sure that that would actually happen.
This behaviour does seem intermittent in that it fired up from cold this morning and ran fine for 5 hours before today's oddness began.
It also seems that if I exercice very fine control between 0 and 1 I can get some level of control of temperature, but I don't think one should need fingers with the sensitivity of a safe-cracker in order drive your central heating.
I'm guessing something is wrong either with the primary temperature sensor thermistor (a cheap fix) or it's a PCB problem. Any thoughts, other than to replace those parts starting with the cheapest?
I am not going to attempt to fix this myself, it's just I like to get my head round things before I engage an engineer.
Finally, there is an inspection hole on the back of the PCB casing which gives access to a couple of pots on the PCB. What does the CH CAP pot do?
Typically I set the CH thermostat in the range 2-4 and the pressure runs between 1 and 1.5 bar.
The behaviour now is that with the CH thermostat at 2 the rads are getting very hot and pressure rises up to 2 bar. Pressure actually seems to be nudging up slowly beyond there. Sometimes turning the thermostat down to zero stops the beast running, but sometimes it needs to be turned off and reset. I've not let it run to an overheat, nor do I know for sure that that would actually happen.
This behaviour does seem intermittent in that it fired up from cold this morning and ran fine for 5 hours before today's oddness began.
It also seems that if I exercice very fine control between 0 and 1 I can get some level of control of temperature, but I don't think one should need fingers with the sensitivity of a safe-cracker in order drive your central heating.
I'm guessing something is wrong either with the primary temperature sensor thermistor (a cheap fix) or it's a PCB problem. Any thoughts, other than to replace those parts starting with the cheapest?
I am not going to attempt to fix this myself, it's just I like to get my head round things before I engage an engineer.
Finally, there is an inspection hole on the back of the PCB casing which gives access to a couple of pots on the PCB. What does the CH CAP pot do?
